The present invention relates to bulk silicon micromachining, particularly to utilizing the parallel etching characteristics of bulk silicon micromachining, and more particularly to integrating the parallel etch planes of silicon with silicon wafer bonding, and impurity doping for etch stops to fabricate on-chip benchtop (miniature) optical systems.
In recent years micromachining of bulk silicon has been developed to a stage wherein a wide variety of micro electromechanical systems (MEMS), such as microvalves, microactuators, and microgrippers have been fabricated using this technology. For several years efforts have been directed to developing miniature silicon optical components using micromachining of bulk silicon.
The main step in bulk silicon micromachining is the patterning and selective etching of the silicon wafers. Often an anisotropic etchant is chosen with which certain crystalline planes within the single crystalline wafer have much higher etch rates than others. Therefore the resultant shape transformed from the lithography pattern exposes the slowest etching crystalline planes. These planes are either parallel to each other or at certain angles to each other. It has been discovered that by using these crystalline planes as micromirrors, miniaturized optical systems can be fabricated, and this invention capitalizes on these in situ parallel micromirrors, thereby eliminating the need for assembly and alignment. Another advantage of utilizing these crystalline planes in bulk silicon is that grooves can be etched for the placement of optical fibers that are also in situ aligned. By the use of existing bulk silicon micromachining which utilizes the crystalline planes of bulk silicon, combined with existing silicon doping/diffusion etch stop and bonding technologies, various miniature silicon optical systems can be fabricated. For example, these combined technologies, when using the crystalline planes of bulk silicon, can be used to fabricate thin film semi-transparent beam splitters, channels not only for light but for liquids as well, for applications such as electrophoresis. Also, integration of these components can be utilized to fabricate optical sensors, detectors, etc. By combining this technology with integrated microactuators, interferometry instrumentation can be fabricated. For example, a miniature optical interferometer integrated on a silicon or glass substrate can now be fabricated utilizing the combination of technologies provided by the present invention.